diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index cddf764..d52a4e9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -16,7 +16,7 @@ jobs:
       matrix:
         toolchain:
           # Don't forget to update the README when bumping MSRV.
-          - 1.56.1
+          - 1.59.0
           - stable
           - beta
           - nightly
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0338195..71a3724 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,9 +1,15 @@
+### v1.4.0 (2023-09-19)
+
+- **Changes**:
+    - Bump minimum supported Rust version to 1.59.0 (released 2022-02-24). This is for compatibility with new versions of some of rangemap's test dependencies.
+
+
 ### v1.3.1 (2023-09-19)
 
 - **Fixes**:
     - Fix `PartialEq`, `PartialOrd`, and `Ord` implementations for `RangeMap` (and `RangeSet`). These previously only compared the starts of ranges instead of the entire range. Thanks to https://github.com/hecrj for finding and fixing this!
 - **Changes**:
-    - Minimum supported Rust version for running this crate's tests has increased (I think to 1.59) due to a corresponding MSRV bump in a test dependency. This is causing CI builds to fail against rustc 1.56.1, but should not affect consumers of the crate. The next minor release (1.4.0) will bump the minimum supported Rust version of rangemap itself.
+    - Minimum supported Rust version for running this crate's tests has increased (I think to 1.59.0) due to a corresponding MSRV bump in a test dependency. This is causing CI builds to fail against rustc 1.56.1, but should not affect consumers of the crate. The next minor release (1.4.0) will bump the minimum supported Rust version of rangemap itself.
 
 
 ### v1.3.0 (2023-01-03)
diff --git a/Cargo.toml b/Cargo.toml
index d254f84..323705a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "rangemap"
-version = "1.3.1"
+version = "1.4.0"
 authors = ["Jeff Parsons <jeff@parsons.io>"]
 edition = "2018"
 license = "MIT/Apache-2.0"
diff --git a/README.md b/README.md
index 188e354..a9aa014 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@
 [![Crate](https://img.shields.io/crates/v/rangemap.svg)](https://crates.io/crates/rangemap)
 [![Docs](https://docs.rs/rangemap/badge.svg)](https://docs.rs/rangemap)
 [![Build status](https://github.com/jeffparsons/rangemap/workflows/CI/badge.svg)](https://github.com/jeffparsons/rangemap/actions)
-[![Rust](https://img.shields.io/badge/rust-1.56.1%2B-blue.svg?maxAge=3600)](https://github.com/jeffparsons/rangemap) <!-- Don't forget to update the GitHub actions config when bumping minimum Rust version. -->
+[![Rust](https://img.shields.io/badge/rust-1.59.0%2B-blue.svg?maxAge=3600)](https://github.com/jeffparsons/rangemap) <!-- Don't forget to update the GitHub actions config when bumping minimum Rust version. -->
 
 [`RangeMap`] and [`RangeInclusiveMap`] are map data structures whose keys
 are stored as ranges. Contiguous and overlapping ranges that map to the same